1. Field of the Invention
This invention generally relates to a system for diagnosing trouble in a pressure device control apparatus which includes: a pressure source having a pump for pumping a fluid from a fluid tank, an accumulator connected to the pump and a pressure device, and a pressure detector for detecting pressure in the accumulator; a normally-closed type solenoid valve interposed between the pressure device and the accumulator or the fluid tank; and a control unit having a drive control means adapted to produce a driving signal indicative of a command to operate the pump in response to a detection pressure detected in the pressure detector becoming equal to or less than a first predetermined pressure and to produce a drive stopping signal indicative of a command to stop the operation of the pump in response to the detection pressure becoming equal to or more than a second predetermined pressure which is higher than the first predetermined pressure.
2. Description of the Relevant Art
A pressure device control apparatus is used, for example, in a hydraulic braking pressure control apparatus for a vehicle as disclosed in Japanese Laid-open Patent Application No. 279499/90, but in this pressure device control apparatus, if, for example, the accumulator breaks down or has a problem, and sufficient pressure cannot be insured, it is difficult to insure the performance of the pressure device. Therefore, it is required to monitor the problem. To this end, it is conventional practice to detect the position of a piston in the accumulator, to constantly monitor the pressure in a back pressure chamber in the accumulator or to detect the elapsed time for an increase in pressure in the accumulator.
In the techniques including the detection of the position of the piston in the accumulator or the constant monitoring of the pressure in the back pressure chamber in the accumulator, a detector is required; thereby, resulting in an increase in the number of parts and an increase in cost and additional technical difficulties. Also, in the technique including the detection of the elapsed time for the increase in pressure in the accumulator, it is difficult to detect the trouble with high accuracy.